package leetCode.q2;

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode() {}
 *     ListNode(int val) { this.val = val; }
 *     ListNode(int val, ListNode next) { this.val = val; this.next = next; }
 * }
 */
public class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode head = null, tail = null;
        int carry = 0;
        while (l1!=null||l2!=null){
            int a = l1 == null ? 0 : l1.val;
            int b = l2 == null ? 0 : l2.val;
            int sum = a+b+carry;

            if(head == null){
                head = tail = new ListNode(sum%10,null);
            }else{
                tail.next = new ListNode(sum%10,null);
                tail = tail.next;
            }

            carry = sum/10;

            if(l1!=null) l1 = l1.next;
            if(l2!=null) l2 = l2.next;
        }
        if(carry>0) tail.next = new ListNode(1,null);

        return head;
    }
}
